As an important research area for tropical marine biodiversity in China, Hainan Province hosts rich mollusca resources. In the report, the research progresses on the diversity characteristics of the mollusks of Hainan Province, the classical and systematic taxonomy, and the major limitations were reviewed. The documented mollusks cover 5 classes, 185 families, and 1 128 species. However, the current research are limited by the morphological misidentification, the scope limitation of the survey, the habitat fragmentation, and the technical constraint in molecular marker applications for phylogenetic resolution. In the future, based on the environmental DNA metabarcoding for biodiversity monitoring, the multidimensional data fusion, and the phylogenomics technology, the high-resolution phylogenetic frameworks can be constructed, the cross-regional collaborations can be strengthen, and the investigation and protection of the mollusca resource can be improved.

In order to elucidate the annual variation of foodborne pathogenic bacteria in commercially available shellfish, in the report, the plate spread method and PCR were used to determine the total bacterial count and the levels of five foodborne bacteria in different tissues of Crassostrea hongkongensis and Perna viridis sourced from Haikou markets. The results indicated that: 1) Apart from Escherichia coli, the levels of other tested bacteria in C. hongkongensis and P. viridis mussels exhibited significant seasonal fluctuations. The total bacterial count and Vibrio vulnificus peaked in August and September; Vibrio parahemolyticus levels in C. hongkongensis were higher in January and July, while those in P. viridis were higher in January and August; Listeria monocytogenes levels in C. hongkongensis were higher between June and August, and those in P. viridis peaked in June; Salmonella levels in C. hongkongensis were higher between May and July, whereas those in P. viridis were higher in July and August. 2) There were certain differences in the levels of foodborne bacteria between C. hongkongensis and P. viridis. In the months with high levels of E. coli, V. parahemolyticus, L. monocytogenes, and Salmonella, the bacterial counts detected in C. hongkongensis were higher than those in P. viridis (9.3×10⁴ CFU·g⁻¹ vs. 5.0×10⁴ CFU·g⁻¹, 7.9×10⁴ CFU·g⁻¹ vs. 6.1×10⁴ CFU·g⁻¹, 2.0×10⁵ CFU·g⁻¹ vs. 1.5×10⁵ CFU·g⁻¹, 5.7×10⁵ CFU·g⁻¹ vs. 3.8×10⁵ CFU·g⁻¹, respectively). Conversely, for V. vulnificus, the detection levels were higher in P. viridis (1.9×10⁵ CFU·g⁻¹ vs. 1.1×10⁵ CFU·g⁻¹). 3) The differences in the levels of different foodborne bacteria among the five tissues of the two shellfish species were relatively small, with slightly higher bacterial levels in the mantle and gills compared to other tissues. Our findings provided the data support for the safe consumption of oysters and mussels.

To detect the carbon contents of common bivalve mollusks in the South China Sea and evaluate the carbon sequestration capacity of bivalve mollusks cultivated in Guangdong, Guangxi and Hainan, this study measured the carbon contents in the shells and soft tissues of 21 common tropical bivalve mollusks. Additionally, based on the carbon contents of these mollusks, a statistical analysis was conducted on the carbon sequestration capacity of bivalve mollusks cultivated in Guangdong, Guangxi and Hainan in 2022. The results showed that the carbon contents of soft tissues in 21 bivalve mollusks ranged from 31.33%~43.20%, with the highest being observed in Sinonovacula constricta and the lowest in Spondylus aurantius; the carbon content of their shells ranged from 11.32% to 14.35%, with the highest in Perna viridis and the lowest in Mimachlamys nobilis; the carbon content of the whole body wet weight ranged from 7.10% to 11.48%, with the lowest content found in Atrina pectinata and the highest in Sinonovacula constricta. The total carbon sequestration capacities of bivalve mollusks cultivated in Guangdong, Guangxi and Hainan provinces in 2022 were 145, 936, 104, 645 and 164 t, respectively; the carbon sequestration capacities per unit area in these provinces were 2.78, 3.14 and 0.15 t·hm⁻², respectively.